Compressing a slow drive for performance?

I've gotten a shiny new computer with just a 60gb SSD, and I don't store much media so it hasn't been a problem... until I bought a game pack that needs 50gb+ to install. With hard drive prices and my wallet as it is, I cannibalized my old laptop for its slow, 5400rpm drive.

I'm wondering if the performance will be better or worse if I compress it. Specifically, I'm hoping I can use this effect, considering that I rarely max out more than 2 of my 4 cores.

Compressing and decompressing a file is processor intensive task (varies a lot depending on file sizes and how frequently files are created/modified).

I dont think compression is going to improve performance.(My guess is it will worsen it)

So i think you would be better off with slow 5400 rpm drive.